Power steering problem

I am working on my ML320 THe power steering line popped off the radiator last week, and now the pump os noisy, I replaced the pump with a brand MB unit ans the new pump is still noisy. I believe there must be some time of restriction in the system, The steering works perfect power and all. Just noisy, Even when reving the engine you hear it ans way worse when turning with the rpm up.

Is the a known problem in the steering system?

Thanks In Advance for the help

Otto